Current digital data transmission techniques involve transmitting one bit of data per unit time. This is the common technique used for transmitting digital information whether the media be hard wire connection (copper), optical fiber (fiber), or radio frequency (RF).
Although computers communicate serially, they typically operate in a parallel data mode. 8-bits, 16-bits and 32-bits are the most common parallel bused systems. In these systems all parallel data lines change states synchronously per unit time. Parallel connections are by far the fastest mode of communications. However, they require physical connections for all the lines. The physical length of the connections are limited as well as the speed of data transfer because of cross talk on the lines, impedance of the wires, and susceptibility to outside RFI/EMI interference. Consequently, the internal parallel buses of a computer are very short. The external connections on parallel buses are also short--typically less than 10 feet. Serial connection on the other hand can be quite lengthy--100s of feet, (enhanced systems such as those used by phone companies can be 100's miles long) partly because there is significantly less interference due to cross talk and the cable being shielded.
There are two types of serial communications--synchronous and asynchronous. In asynchronous serial communications the computer transfers data to a device having an n-bit storage register. This device also has an external clock that is used to synchronize the data transmission between the computer and the transmitting device. The transmitting device shifts one data bit, the least significant bit, onto a single output line, counts a specified number of clock pulses, shifts the next bit on the transmitting line, counts the specified number of clock pulses, and continues until all n data bits are transmitted. The transmitting device then indicates to the computer it is ready to transmit another n-bit byte. The cycle continues until all data is transmitted.
At the receiving end, when the receiver senses that it is receiving data it counts half of the specified number of clock pulses, then samples the data again--if the state has not changed the receiver assumes it is receiving a data byte and the first data bit is shifted into an n-bit shift register. The receiving device then counts the specified number of clock pulses and shifts whatever is on the receiving line into the shift register. The first bit received is shifted one bit position. This continues until all bits of the word are received.
At this time the receiving computer is notified that data can be received. There are start and stop bits that help the receiver determine that data is being received properly, and there are numerous forms of software flow control bytes in the data. In short length serial lines, typically less than 25 feet, there may also be additional hardware control lines used to determine when data should be transmitted.
In synchronous serial communications, one computer or the other generates the clock signal and this signal is transmitted over a physical connection between the two devices. This allows for higher speeds as the receiver can store bits on every clock pulse as opposed to sampling at what is assumed to be the middle of each transmitted bit (this is why the first bit is stored on half of the clock pulses and every bit there after at the specified number of clock pulses as previously explained).
The transmission of parallel based computer generated information via copper, fiber, or RF from one location to another requires that the parallel data be converted to a serial format prior to transmission. Over the years the transmission speeds have increased significantly in order to transmit serial data at higher data rates.
There is a need for an enhanced method of digital data transmission that would increase the speed of parallel data transmitted without being transformed into a serial mode. Such a parallel transmission method would significantly increase data transmission rates, allow for more users on a network (or callers on a phone system using the same time-division multiplexed protocols currently in use), and provide for new communications system developments to accommodate increased usage.
In addition to serial and parallel mode communications, dual tone multiple frequency mode (DTMF) communications are also being used. One use of DTMF is for generating digital tones on phone sets. This system allows the phone system to determine which of the twelve keys on a phone key pad has been pressed. DTMF assigns a unique frequency to each row and column on a telephone keypad. When a key is pressed the associated row and column frequencies are mixed and transmitted over the telephone wire. The receiving end, through the use of filters determines which of the frequencies were originally transmitted and thus determines which key was originally pressed.
There is also wireless data communication that uses conventional techniques. Typically in wireless data communication a carrier frequency is used to carry the data in a manner similar to that used by AM and FM radio transmissions. A local oscillator at the transmitter generates the signal that is transmitted from the antenna. The signal, typically voice, is beat or mixed or modulated with the local oscillator signal. The voice signal is at a much lower frequency than that of the local oscillator signal. At the receiver end a receiving local oscillator is tuned to exactly the same frequency as that of the transmitting local oscillator signal, but the signal generated is 180 degrees out of phase. The mixed signal transmitted is mixed with the receiving local oscillator signal causing the mixed signal transmitted to be stripped of the transmitting local oscillator signal. The remaining signal represents that which was originally mixed with the transmitter local oscillator signal. This signal is amplified and sent to a speaker.
This type of radio frequency transmission method can used to transmit computer data. Because the local oscillator signal is a single frequency, data can be transmitted in a manner considered serial. This is because the data is mixed with the local oscillator signal and transmitted in the same method as explained in the serial discussions above. One bit at a time is mixed with the local oscillator signal for a given period of time. Data is received and reconstructed as described above.
It is the object of the present invention to enhance computer data transmission time by providing a device that transfers and reconstructs an n-bit digital data word in a period of time equal to that used to transmit one data bit in parallel to serial communications.